In the oil industry, produced water is a term used to describe water that is produced along with the oil and gas. Produced water may come from various sources. For example, oil and gas reservoirs have a natural water layer that lies under the hydrocarbons. Also, water may be injected into reservoirs to help force oil to the surface. This water is produced along with the oil and/or gas when the latter is extracted. Produced water is considered an industrial waste, and therefore, careful disposal is necessary. Historically, produced water was disposed of in large evaporation ponds. However, this has become an increasingly unacceptable disposal method from both environmental and social perspectives. The broad management options for produced water include direct injection, environmentally acceptable direct-use of untreated water, or treatment to a standard defined by the U.S. Environmental Protection Agency (EPA) before disposal or supply to users.
Management of produced water can be problematic. For example, disposal through direct injection may not be feasible. Typically, large-scale on-site storage and/or disposal require significant investment costs towards large and expensive infrastructure. Trucking water off-site for disposal involves high transport costs. Therefore, cost efficient, on-site solutions to produced water disposal and management are sought.
Evaporation technologies are known in the art, but current designs have significant drawbacks. For example, produced water can be evaporated at small on-site evaporation ponds. While relatively low-cost, these ponds still create relatively large surface-area disturbance and they may also be attractive and/or harmful to wildlife. Also, water may be sprayed into the atmosphere through portable misting towers. But, misting can lead to salt damage to soil and vegetation. Evaporation may be achieved by introducing thermal elements into smaller volumes of water to speed evaporation. But, the resulting precipitates tend to create scaling, which adheres to heating elements over time, reduces efficiency, and creates maintenance issues. Therefore, efficient and environmentally safe solutions for the evaporative disposal of produced water are elusive.